When zoo bosses decided to invest in a Thomas the Tank Engine train for their young visitors, naturally they wanted a Fat Controller too.
So they decided to advertise for a portly gentleman who might fit the bill. That's where the problems started.
The zoo's legal advisers warned that advertising specifically for a fat man could be considered illegal.
They told officials at Drusillas Park Zoo in East Sussex that they should not discriminate - and might have to interview a thin man if one applied for the job. The zoo launched the ride last month, after importing Thomas from Germany, complete with versions of the carriages Annie and Clarabel.
Managing director Laurence Smith said a member of staff had been filling in as the driver on occasions.
"But at a slim 15st he doesn't quite fit the specification."
Christine Smith, his wife, is also a managing director at the zoo, at Alfriston, near Eastbourne.
She said: "Since we did the deal to bring Thomas to Drusillas we have worked very hard to ensure the train and all the theming is an exact replica of the books and the TV programme.
"So getting a fat Fat Controller is just part of that commitment. We are hoping that common sense will prevail and that we will find the right person before too long. We are currently advertising the part-time job on our website but have had to be very discreet about what we say."
John Midgley, co-founder of the Campaign Against Political Correctness, said: "Why on earth should this park, that is trying to do its best to keep faithful to books, that have been enjoyed by generations, be penalised by the politically-correct lobby?
"It is so ridiculous. I really can't think the vast majority of common-sense people would take the slightest offence over this. It is no wonder, that in a national opinion poll carried out by ICM for the campaign, 80 per cent of Britons are fed up with political correctness."
The Fat Controller's official name is Sir Topham Hatt.